public class BinarySearchTree {
    static class TreeNode{
        public int val;
        public TreeNode left;
        public TreeNode right;
        public TreeNode(int val){
            this.val=val;
        }
    }

    public TreeNode root=null;

    //查找二叉搜索树中指定的val值
    public TreeNode find(int val){
        TreeNode cur=root;
        while (cur!=null) {
            if(cur.val<val){
                cur=cur.right;
            }else if(cur.val==val){
                return cur;
            }
        }
        return null;
    }

    //插入一个数
    public void insert(int val){
        if(root==null){
            root=new TreeNode(val);
            return;
        }
        TreeNode cur=root;
        TreeNode parent=null;
        while (cur!=null){
            if(cur.val<val){
                parent=cur;
                cur=cur.right;
            } else if (cur.val==val) {
                return;
            }else {
                parent=cur;
                cur=cur.left;
            }
        }
        TreeNode node=new TreeNode(val);
        if(parent.val<val){
            parent.right=node;
        }else {
            parent.left=node;
        }
    }

    public void inorder(TreeNode root){
        if(root==null){
            return;
        }
        inorder(root.left);
        System.out.print(root.val+" ");
        inorder(root.right);
    }

    //删除val的节点
    public void remove(int val){
        TreeNode cur=root;
        TreeNode parent=null;
        while (cur!=null){
            if(cur.val==val){
                removeNode(parent,cur);
                return;
            } else if (cur.val<val) {
                parent=cur;
                cur=cur.right;
            }else {
                parent=cur;
                cur=cur.right;
            }
        }
    }
    private void removeNode(TreeNode parent,TreeNode cur){
        if(cur.left==null){
            if(cur==root){
                root=cur.right;
            } else if (parent.left==cur) {
                parent.left=cur.right;
            }else {
                parent.right=cur.right;
            }
        } else if (cur.right==null) {
            if(cur==root){
                root=cur.left;
            } else if (parent.left==cur) {
                parent.left=cur.left;
            }else {
                parent.right=cur.left;
            }
        }else {
            TreeNode target=cur.right;
            TreeNode targetParent=cur;
            while (target.left!=null){
                targetParent=target;
                target=target.left;
            }
            cur.val= target.val;
            if(target==targetParent.left){
                targetParent.left=target.right;
            }else{
                targetParent.right=target.right;
            }
        }
    }

}










